It remains uncertain what causes the slight brightening. However, Tsumura and his colleagues believe the upper part of Jupiter's atmosphere may be responsible.
Jupiter's clouds, which give the giant planet its striped appearance, grow from tiny particles called aerosols or hazes. Prior studies have hinted that these hazes form in the upper part of Jupiter's atmosphere. The researchers suggested that hazes in the upper atmosphere may scatter sunlight onto the Galilean satellites, illuminating them. This effect is similar to the one that causes Earth's moon to look red during a total lunar eclipse.
The new finding could help scientists analyze the hazes in Jupiter's atmosphere, which are otherwise difficult to study. By studying the spectrum of light from the eclipsed Jupiter moons, the researchers could learn about the compositions of the hazes, Tsumura said.
In addition, this new method of studying Jupiter's upper atmosphere could help researchers investigate the atmospheres of exoplanets around distant stars. Exoplanets are often seen when they pass in front of their stars, and scientists can glean details about their atmospheres when starlight passes through them.
"It is important to study sunlight transmitted through the atmospheres of the planets in our solar system for comparison with light through the atmospheres around the exoplanets," Tsumura said.
Tsumura and his colleagues detailed their findings in the July 10 issue of The Astronomical Journal.
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